1. Field of the Invention
The present invention relates to a semiconductor laser; specifically to a semiconductor laser equipped with a waveguide ridge.
2. Background Art
The present invention relates to a semiconductor laser used in an optical disk system, optical communications, or the like: more specifically to a discrete and monolithic semiconductor laser with a double-channel type ridge structure. The double-channel type ridge structure means the configuration wherein a ridge is sandwiched between channel (trench) portions having a low equivalent refractive index, and the channel portions are further sandwiched between layers having a high equivalent refractive index (for example, refer to Japanese Patent No. 3857294, FIG. 13).
With the rise of output of laser beams, a flare-type laser having a ridge structure, wherein the ridge width is varied in a laser resonator and the ridge width is widened toward the light outgoing end surface, has been adopted. This structure has advantage to realize high output, as well as to lower the device resistance, operating voltage, and operating current. The channel width of conventional lasers having a flare ridge type double channel structure has been designed to have a constant value regardless of the variation of ridge width (for example, refer to Japanese Patent Application Laid-Open No. 2006-303267, Japanese Patent No. 2695440, National Publication of International Patent Application No. 2005-524234).